Scope - bore measurement

Guys,
How critical is the exact height above bore measurement of a scope in calculations of the ballistics of a load? I'm using Sierra Infinity 5 and Exbal. What is the best way to measure it? I have in the past just tried to measure this by using a ruler and eyeballing it. I know y'all must have a more accurate way. Thanks for your response.
Paul

The center of bore to center of scope measurement is not super critical but does play an effect. For instance a 6.5mm 140g A-Max traveling 3000fps at an altitude of 1500 with a center of bore to center of scope distance of 2 3/4" with a 100 yard zero has a drop value of 24.4 moa at 1000 yards and 99.6 at 2000 yards. Now if all we change is the sight height to say 3", the drop value of the same bullet at 1000 yards is 24.2 moa and 2000 yards is 99.4 moa. A mere 1/4 moa. So you should be able to measure center of bore to center of scope with using a ruler and come very close without it making a huge difference.

Guys,
How critical is the exact height above bore measurement of a scope in calculations of the ballistics of a load? I'm using Sierra Infinity 5 and Exbal. What is the best way to measure it? I have in the past just tried to measure this by using a ruler and eyeballing it. I know y'all must have a more accurate way. Thanks for your response.
Paul

Like has been said, it's not overly critical but get as close as you can. You can measure the barrel dia. and the scope dia. and take half of each, then add the distance between the scope and barrel to the two radius measurements mentioned and you would be about as close as you could get. Just remember to take the dia. measurements on the same vertical plane so that the measurements at least make some sense.;)